1. Field of the Invention
The present invention relates to a nonaqueous emulsified surface treating agent composition which comprises a fluorine-containing-oil-in-hydrocarbon-containing-oil emulsion (hereinafter referred to as F/H emulsion) containing a polymeric surfactant.
2. Related Art
Since a fluorine-containing oil such as a perfluoropolyether, a polychlorotrifluoroethylene and a fluorocarbon can provide a good lubricity and a high water- and oil-repellency, it is frequently diluted with a fluorine-containing solvent to be used as a surface treating agent. With the prohibition of a restricted fluorocarbon, it is desirable to use a hydrocarbon solvent as the solvent for the surface treating agent. But, the fluorine-containing oil does not dissolve or disperse in the hydrocarbon solvent. If an emulsion in which the hydrocarbon-containing oil is a continuous phase and the fluorine-containing oil is a dispersed phase, namely a F/H emulsion can be prepared, it can be dissolved with the hydrocarbon solvent so that it can be sufficiently used.
A conventional surfactant has a hydrophobic group (a hydrocarbon group, a fluorine-containing alkyl group and a silicone group) and a hydrophilic group in one molecule. The conventional surfactant is synthesized in view of the use in the aqueous phase having the objects that a surface tension of aqueous phase decreases and an interfacial tension between aqueous and oily phases decreases. When this type of surfactant is used to prepare the F/H emulsion, the surfactant is not effectively adsorbed by a hydrocarbon-containing oil/fluorine-containing oil interface so that a stable emulsion cannot be obtained, since the hydrophilic group in the molecule has no affinity for both of the hydrocarbon-containing oil and the fluorine-containing oil. The surfactant molecule must have a fluorine-containing compound group and a hydrocarbon compound group so that the surfactant is effectively adsorbed by the hydrocarbon-containing oil/fluorine-containing oil interface. Such a surfactant is herein referred to as "R.sub.f -R.sub.h surfactant."
The preparation of the F/H emulsion using the R.sub.f -R.sub.h surfactant was attempted in Japanese Patent Kokai Publication Nos. 292713/1987 and 2916/1988. However, a surfactant having low molecular weight perfluoroalkyl group and hydrocarbon alkyl group in the molecule is used, and the surfactant is adsorbed by the interface and gives an emulsion, but a stable emulsion can not be obtained. When the reason for this is studied in view of a principle of emulsion destruction, the following matters are believed to be the reasons. The main reason for emulsion destruction is an aggregation and cohesion. It is known that the aggregation is prevented by a static repulsion force or steric hinderance repulsion force of emulsion particle surface and the cohesion is prevented by the viscoelasticy of continuous phase/dispersed phase interfacial film. In the conventional F/H emulsion, the repulsion force among the particles is a steric hinderance force caused by the hydrocarbon alkyl group extending from the emulsion particle surface into the hydrocarbon-containing oil. Since the low molecular weight surfactants of the above patent publications have a short chain, the repulsion force among the particles caused by the steric hindrance force is weak. Since the surfactant itself has a low molecular weight, the interfacial viscoelasticy is low so that the cohesion among the particle easily occurs.
As stated above, none of the conventional F/H emulsions has sufficient long-term stability.